The present invention relates to a digital video tape recorder and, more particularly, to apparatus for recording and reproducing a video signal and an audio signal in the form of coded signals on a recording medium.
Digital video tape recorders which record and reproduce video and audio signals in coded form are known in the art. These digital video tape recorders often employ efficient coding techniques for compressing the amount of data to be recorded. Among these techniques, discrete cosine transformation (DCT), is commonly employed. It has been proposed that identification (ID) signals be used to distinguish between various recording and reproducing modes including standard play (SP) mode and long play (LP) mode. However, since the data recording format that may be employed is limiting, various types of data in various types of structures cannot be recorded and reproduced easily.
Digital audio tape (DAT) recorders attempt to solve this problem with respect to audio signals. In a typical DAT data structure, an identification area of 2 bits.times.2 areas (4 bits) is provided at every synchronizing period in the main data area. Data representing, for example, the presence or absence of emphasis, sampling frequency, number of channels and quantization method, can be recorded or reproduced with the identification data. The identification areas thus may identify what the accompanying data represents.
In the above-mentioned DAT data structure, so-called subcode areas are provided at respective ends of each track recorded on the record tape. Identification data accompanying the audio signals are recorded on and reproduced from these subcode areas. Eight blocks of such data are recorded in the subcode area. Of these eight blocks, even-numbered blocks of eight bytes each contain seven bytes of data and one byte of parity code. Upon reproduction of the even-numbered blocks, error correction is accomplished by utilizing what has become known in the art as inside parity and outside parity. Odd-numbered blocks contain four bytes of other identification data, and upon reproduction, error correction is carried out only by the outside parity. Thus, the ID area, the even-numbered blocks and the odd-numbered blocks of the main data area have different data structures. Therefore, the software necessary to process this data is complicated.
Further, since the timing with which the aforementioned DAT data in the ID area, the even-numbered blocks and the odd-numbered blocks is recorded and reproduced is different due to the different data structures, a memory, such as a random access memory (RAM), is necessary to record and reproduce the audio signals. Furthermore, when new DAT equipment is developed, the software utilized with existing DAT recorders might not be able to be used and new software is expensive to develop.
Thus, mere modification of the data structure used in the aforementioned digital audio tape recorder to allow for recording and reproduction of video data would be unsatisfactory to a user since this VTR would be capable of only performing "basic" functions and would not be capable of performing a multitude of other functions which have become standard in video tape recorders and in addition, would not contain features present in the digital video tape recorder of the present invention.